81665532 has 108 divisors (see below), whose sum is σ = 231276864. Its totient is φ = 24261120.

The previous prime is 81665513. The next prime is 81665543. The reversal of 81665532 is 23556618.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 188388 + ... + 188820.

Almost surely, 2^81665532 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81665532, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115638432).

81665532 is an abundant number, since it is smaller than the sum of its proper divisors (149611332).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81665532 is a wasteful number, since it uses less digits than its factorization.

81665532 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 500 (or 482 counting only the distinct ones).

The product of its digits is 43200, while the sum is 36.

The square root of 81665532 is about 9036.8983617168. The cubic root of 81665532 is about 433.8566566331.

The spelling of 81665532 in words is "eighty-one million, six hundred sixty-five thousand, five hundred thirty-two".